1. Field of the Invention
The present invention relates to a fuel tube in which fuel such as gasoline, alcohol gasoline or sour gasoline flows.
2. Description of the Related Art
There is a demand for a fuel tube having a good balance between the two characteristics of low permeability to fuel such as gasoline and high flexibility for handling property. Although fuel permeability of the fuel tube can be reduced when a low fuel permeability resin such as a polyphenylene sulfide resin (hereinafter referred to as PPS resin) or a polymetaxylylene adipamide resin (hereinafter referred to as MXD6 resin) is used for forming the fuel tube, the fuel tube lacks flexibility because a material low in fuel permeability is generally high in elastic modulus. The easiest method for improving the flexibility is to use a mixture composition prepared by adding an elastomer component to a low fuel permeability resin. In this method, however, fuel permeability becomes high.
Therefore, an intention to laminate an inner layer of a low fuel permeability resin and an outer layer of a low elastic modulus material has been heretofore examined to obtain a good balance between the two characteristics. For example, a fuel tube having an inner layer made of a PPS resin and a functional group-containing thermoplastic resin, and an outer layer made of another thermoplastic resin than the PPS resin has been described in JP-A-10-138372. A fuel tube having an inner layer made of a resin composition containing a metaxylylene group-containing polyamide resin and a modified polyester elastomer, and an outer layer made of a polyester elastomer has been described in JP-A-4-86257. A fuel tube having an inner layer made of a low fuel permeability resin such as a PPS resin, and an outer layer made of a thermoplastic elastomer has been described in JP2000-329266A.
In such a fuel tube produced by lamination, the inner layer and the outer layer need to be bonded to each other by sufficient interlayer adhesive power so as not to be separated easily. It is however impossible to obtain sufficient interlayer adhesive power between the inner layer and the outer layer self-bonded to each other by direct contact because adhesion between the material of the inner layer and the material of the outer layer in the fuel tube produced by lamination in the related art low. It is therefore necessary to interpose an adhesive agent between the inner layer and the outer layer or add an adhesive agent into each of the materials of the inner and outer layers.